A police marksman who shot at barrister Mark Saunders today wept as he told the inquest jury: "I didn't want to kill anyone."

The officer, known as AZ7, could be heard choking with emotion, sobbing and sniffing heavily as he gave evidence behind a screen protecting his identity from the public and press.

He described his feelings as Mr Saunders lowered his shotgun twice as he leant out of the kitchen window of his Chelsea home during the five-hour police siege in May 2008.

The first time the police did not open fire even though the shotgun was pointing in their direction. Said AZ7: "I thought he was actually going to shoot me. I started squeezing the trigger."

Suddenly Mr Saunders raised the barrel of the gun upwards so that it was pointing at the sky and was no longer a threat.

"I was so relieved and I released the pressure on my trigger," said AZ7 through his tears. "I wanted to give him every possible chance to drop the gun but there's only so far you can go.

"In my mind if he had wanted to pull the trigger at that point it would be too late and I would be dead."

But seconds later Mr Saunders slowly lowered the barrel again.

"The barrel came down a second time. I didn't really think I had any room for error," said the officer.

"He looked more comfortable and seemed to settle himself into his stance. I could see the end of the barrel pointing at me and I decided I needed to fire my weapon for my own protection and the protection of the two guys to my right (police colleagues). As my gun went off, and I can't tell you why, I believed he had fired at the same time. There was lots of noise, lots of smoke.

"I didn't want to kill anyone. I wanted to give him as much chance as he needed but his body language suggested to me, and his initial movement with the gun, that he was not surrendering but was settling into a better shooting stance. It was just milliseconds."

Asked why he had not just taken cover, the officer emphasised he had to maintain eye contact with the armed man to protect other unarmed colleagues and the public. "To hide, I believe, would have been a neglect of my duty and a neglect as a human being," he said.

Another officer, AZ2, told the jury he fired three shots because he said Mr Saunders still seemed to be standing and pointing the gun at him.

Yet seconds earlier he had tried to save the barrister's life by attempting to stop his colleagues shooting.

He heard his colleague AZ10 shout: "F***ing hell," but AZ2 immediately shouted back: "No, it (the shotgun) is pointing at the sky." But then the situation changed.